Called support weeks ago and after a lot of phone calls and emails, I informed MS that they can close the support ticket.
The issue was that I couldn't use my O365 login (MS business/org account) to log into Microsoft Office Mobile App. It would work with my personal MS account.
They said it was because I had the same address for both. However on the web, or with Android apps such as OWA, Outlook, Word and Excel worked with my O365 Account.
Earlier this week I read an article about new Android Apps and now the Office Mobile app says:
*** Try the new Word, Excel, and PowerPoint apps! Now available for Android tablets and phones in the Google Play store: http://aka.ms/worda, http://aka.ms/excela, http://aka.ms/ppta. These new apps replace Office Mobile. **
Microsoft Office Mobile is the Office companion for phones running Android OS prior to v4.4.”
So since my phone is 4.4.2, it's not supposed to work.